Pipe construction system

ABSTRACT

A pipe construction system which utilizes a multiplicity of arcuate pipe segments  11, 12  to form a pipe section  10  and which sections are assembled together to form a length of pipe. Each segment  11, 12  has two longitudinal edges  13  of increased radial thickness and having a groove  14  formed in the circumferential direction whereby an interlocking and sealing member  15  may be located in the aligned grooves  14  of two adjacent segments  11, 12.  One end of a pipe section  10  assembled from the segments defines a socket  22  for receiving a spigot  23  defined at the other end of a like section. The spigot end of each segment has a pocket  25  formed along said edge  13  but within the thickness of the major area of the segment, which pocket  25  mates with a corresponding pocket  25  of an adjacent segment whereby sealant may be disposed in the mating pockets.

TECHNICAL FIELD

This invention relates to a pipe construction system and also to amethod for constructing a pipe from a multiplicity of pipe segments.Certain aspects of this invention concern the lining of an undergroundsewer, using the pipe construction system.

BACKGROUND OF THE INVENTION

In the following description and explanation of this invention,reference will be made primarily to the lining of underground sewers,though it is to be understood that the pipe construction system of thisinvention is not limited to this application, and may be used for a verywide range of different applications. For example, the system may beused to construct an overland or underground pipe, as well as to line awide variety of ducts, so long as the duct is sufficiently large topermit access by human operators, to effect the lining method.

Many underground sewers in major cities throughout the world wereconstructed more than 100 years ago. Consequently, those sewers are bynow becoming very worn internally, with the brickwork or otherconstructional materials deteriorating in view of the nature of theliquids and gases present within the sewer. Further, due to groundmovements over the years, the structural integrity of those sewers canbe seriously compromised. These aspects can lead to failure withinsewers, by the walls of the sewers collapsing inwardly. The consequentremedial work necessary to restore the sewer is extremely difficult andunpleasant to perform, since by the time such work is commenced, thereis likely to be a large volume of sewage backed up behind a blockagecaused by the failure.

It is known to provide a lining within underground ducts such as sewers,in an attempt to restore integrity to the structure. Such a liningtechnique may be performed before there is a catastrophic failure, byopening the sewer at a convenient point and then fitting into the sewerrelatively short lengths of pipe which are connected togetherend-to-end. In the case of a sewer of circular cross-sectional shape,such short lengths of a pipe may be a sliding fit within the existingsewer so that no further work is required. Alternatively, the externaldiameter of the assembled pipe may be significantly less than theinternal diameter of the sewer and then a grouting material is injectedunder pressure into the generally annular space between the pipe and theinternal sewer wall.

Particularly in the case of relatively large sewers, it is also known toassemble a lining from short lengths of pipe which lengths themselvesare assembled from segments each of part-circular shape. One widely usedsystem employs a tongue along one axially-extending edge of a segmentand a correspondingly formed groove along the other axially-extendingedge of a segment whereby the segments may be assembled together withthe tongue of one segment fitting into the groove of the next adjacentsegment. This system has the disadvantage that the strength of thesegments is much reduced in the area of the inter-fitting tongues andgrooves resulting in a relatively weak joint between adjacent segments.Further, it is necessary axially to slide the last segment (or thesecond segment, where two semi-circular segments form the pipe section)into position and during this sliding movement, there is a relativelyhigh risk that the tongue or one of the groove walls will be broken awayfrom its segment.

An alternative but similar system uses butt or halved joints betweenadjacent lining segments, each of which joints is reinforced with anelongate internal cover plate secured over the joint. Such a system isslow and inconvenient to install, especially within the confined workingspace of a sewer.

A disadvantage of the above systems is that the strength and water-tightintegrity of a pipe assembled as described is relatively low and so thesystems are unsuitable for use other than in a grouted pipe-liningsituation, where the strength may be enhanced by the surrounding groutand already existing duct or sewer. Even so, the joint could still leakand over a period of time and so deteriorate the integrity of thesurrounding grout.

It has been proposed to strengthen the longitudinal joints betweenadjacent segments by enlarging the wall thickness in the region of thejoints but in order to give a smooth internal surface to the finishedpipe, all such enlargement must be effected externally of the pipe.However, this then gives rise to a problem at the ends of the pipesections where the end of one pipe section forms a spigot which fitsinto a socket formed at the opposite end of the next adjacent pipesection. The enlarged wall thickness must be cut away and this leads toa very weak area of the assembled pipe, which also is highly likely toleak.

SUMMARY OF THE INVENTION

The present invention has as a principal object the provision of a pipeconstruction system which at least mitigates the disadvantages of theknown form of segmented lining systems as discussed above, and so whichmay be used not only for pipe lining, but also to construct pipe linesin general, for use either above or below ground, as may be required.

Accordingly, one aspect of the present invention provides a pipeconstruction system comprising: a multiplicity of arcuate pipe segmentsa plurality of which may be assembled together to form a pipe sectionwhich defines at one end a socket for receiving a spigot defined at theother end of a like section also assembled from a plurality of saidsegments whereby a length of pipe may be built up from the assembledsections, each segment having two edge regions parallel to the length ofthe pipe section each of which edge regions is of increased radialthickness and is formed with a groove extending from the socket end upto the spigot-forming end of the segment, and at the spigot forming endof a segment there is formed a pocket along said edge but within thethickness of the major area of the segment which pocket mates with acorresponding pocket of the adjacent segment whereby a sealant may bedisposed in the mating pockets.

It will be appreciated that with the pipe construction system of thisinvention, the formation at both axially-extending edges of each segmentshould be essentially the same. By providing the edge regions with anincreased radial thickness, that formation may be made sufficientlystrong and certainly no weaker than the strength of the major area ofthe segment and thus the likelihood of damage to those formations isgreatly reduced, both during handling of a segment prior to assembly toform a pipe section within a sewer, and as the segment is assembled intoa pipe section. Subsequent to the assembly of the segments into a pipesection, a setting or curing sealant compound may be injected into themating grooves, thereby to effect a seal between the segments and alsoto lock together the segments, once the compound has set or cured, asappropriate.

Preferably, each said groove is of re-entrant form whereby the compound,once cured or set, is mechanically held in the two aligned grooves. Onepreferred form of groove is of dovetail cross-sectional shape, wherebythe cured or set compound forms a mechanical interlocking member of acorresponding profile, in effect having two dovetail portions with thenarrower ends thereof joined together. The compound also performs thesealing function as discussed above.

Curing or setting compounds can be made from a suitable resin systemwhich may be reinforced with fibre strands and fillers, the systemensuring that a homogeneous composite structure is formed following thecasting of the bonding interlocking member.

The pockets along said edges of each segment must open through therespective edge itself, in order that the pocket may mate with thepocket of the next adjacent segment to be assembled thereto. In theevent that each such pocket also opens through the end face of thesegment, the sealant may be injected into the mating pockets through theend face openings thereof. Alternatively, where each pocket is closedexcept for its opening through the axial edge of the segment, sealantmay be injected into the mating pockets by drilling a hole into themating pockets either from within the assembled pipe section or fromoutside (depending upon the intended use of the assembled pipe) and thenthe sealant injected through that drilled hole.

Each pocket preferably extends in the axial direction either from theadjacent end face of the segment or a position closely spaced therefrom,towards the other end of the segment for a sufficient distance such thatthe pocket terminates in the general region of the increased thicknesspart of the segment. The sealant does not need to have a high strengthsince the encircling part of the socket of the next adjacent pipesection will confer sufficient strength on the assembly. Thus, thesealant may be in the form of a conventional mastic.

In one possible system of this invention, the groove on each axiallyextending edge of a segment is defined by a pre-formed component bondedto the respective edge of a segment during the manufacture thereof. Sucha pre-formed component may comprise a plastics material moulding,reinforced as appropriate with fibres or the like extending along thelength of the component. The major part of each segment may alsocomprise a fibre-reinforced plastics material moulding such as ofglass-reinforced plastics material. In an alternative construction, themajor part of each segment has inner and outer skins each of a glassreinforced plastics material and a filled plastics material (such as asand-filled plastics resin) being disposed between the skins.

In order to enhance the integrity of the longitudinal joint between twosegments, a reinforcing strip may be laid over the joint, eitherexternally, internally, or both externally and internally, at the timeof assembling the segments together. Conveniently, such a strip issecured to one segment to run along but project from the longitudinaledge of the segment, before assembly of that segment to another. Then,when assembled to the other segment, the strip is also secured to theother segment, to cover the joint. The strip could be clamped in placefor example using mechanical fasteners such as screws, perhaps with aclamping bar, or could be bonded using a suitable adhesive.

The reinforcing strip may be of a fibre-reinforced plastics material,and is advantageously fitted before the casting of the interlockingmember. In this case, the strip may ensure that during the interlockingmember casting step the sealant material is contained mostly within theinterlocking grooves, and so does not escape from these grooves to anysubstantial extent. Also, following completion, the strip will addfurther strength and reinforcement to the longitudinal joint.

During assembly of the pipe from the sections, a suitable mastic, othersealant or a gasket may be applied to the complete socket before thenext section to be assembled is fitted thereto, again to conferwater-tightness to the completed pipe.

According to a second aspect of this invention, there is provided amethod of constructing a pipe from a multiplicity of arcuate pipesegments a plurality of which may be assembled together to form a pipesection which defines at one end a socket for receiving a spigot definedat the other end of a like section also assembled from a plurality ofthe segments whereby a length of the pipe may be built up from theassembled sections, each segment having two edge regions parallel to thelength of the pipe section each of which edge regions is of increasedradial thickness and is formed with a groove extending from the socketend up to the spigot-forming end of the segment; and at the spigotforming end of a segment there is formed a pocket along said edge butwithin the thickness of the major area of the segment which pocket mateswith a corresponding pocket of the adjacent segment; in which method:

-   -   a pipe section is assembled from a plurality of the segments by        aligning said grooves along adjacent segment edges;    -   a setting or curing sealant compound is injected into each pair        of aligned grooves and is allowed to set or cure to provide a        bonding interlocking member;    -   a sealing agent is furnished in the mating pockets at the spigot        end of the section;    -   a further section is assembled in a like manner;    -   sealant is disposed at least one of internally around the socket        of one section or externally around the spigot of the other        section; and    -   the socket of one section and the spigot of the other section        are interengaged.

According to a further but closely related method of constructing a pipefrom a multiplicity of arcuate pipe segments a plurality of which may beassembled together to form a pipe section which defines at one end asocket for receiving a spigot defined at the other end of a like sectionalso assembled from a plurality of the segments whereby a length of thepipe may be built up from the assembled sections, each segment havingtwo edge regions parallel to the length of the pipe section each ofwhich edge regions is of increased radial thickness and is formed with agroove extending from the socket end up to the spigot-forming end of thesegment; and at the spigot forming end of a segment there is formed apocket along said edge but within the thickness of the major area of thesegment which pocket mates with a corresponding pocket of the adjacentsegment; in which method:

-   -   a pipe section is assembled from a plurality of the segments by        aligning said grooves along adjacent segment edges;    -   a setting or curing sealant compound is injected into each pair        of aligned grooves, and is allowed to set or cure to provide a        bonding interlocking member;    -   a sealing agent is furnished in the mating pockets at the spigot        end of the section;    -   sealant is disposed either internally around the socket of the        section or externally around the spigot thereof;    -   the segments of a further section are fitted into the socket or        around the spigot of the already assembled section, to assemble        a further section in a like manner but coupled to the already        assembled section; and then    -   a setting or curing sealant compound is injected into each pair        of aligned grooves of the further section, and is allowed to set        or cure; and    -   a sealing agent is furnished in the mating pockets at the spigot        end of the section.

According to yet another aspect of this invention, there is provided amethod of lining an existing closed duct comprising effecting withinthat existing closed duct a pipe construction method of this inventionas described above so as to build up the pipe in situ in the duct butwith clearance between the outer wall of the pipe and the inner wall ofthe duct, and then filling that clearance with a grouting material.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, one specific embodiment of a pipe constructionsystem of this invention will now be described in detail, referencebeing made to accompanying drawings, in which:-

FIG. 1 is a diagrammatic side view of a section of a pipe made up from apipe construction system of this invention, using two semi-circularsegments to make up the section;

FIG. 2 is a cross-section through the pipe of FIG. 1;

FIGS. 3 and 4 are detailed cross-sections on an enlarged scale, throughthe pipe section of FIG. 1, taken on lines II—II and III—III marked onthat Figure; and

FIG. 5 is a further cross-section through the joint between adjacentlong edges of two segments, showing additional details.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The embodiment of pipe construction system shown in the drawings isintended for lining an already existing underground sewer having atypical diameter in the range of 800 mm to perhaps 2500 mm or more.Though a circular pipe is shown, for use with a sewer of circularcross-sectional shape, the system may be manufactured to have othercross-sectional shapes to suit a sewer being lined—for example, manysewers are of egg-shaped cross-section and the segments making up eachsection of the pipe may be suitably profiled so that the assembledsection has a corresponding cross-section.

In FIGS. 1 and 2, the section 10 of a pipe is shown assembled from twosegments 11, 12, each of semi-circular cross-sectional shape, wherebythe assembled section is of circular cross-section. Eachlongitudinally-extending edge 13 of each segment has an enlargedthickness and defines a groove 14 of dovetail cross-sectional shape. Thealigned adjacent edges 13 of the segments are connected together bymeans of an interlock member 15 cast in-situ in the grooves, byinjecting into those grooves a setting or curing sealant component suchas an epoxy resin compound. The interlock member thus has a doubledovetail form, with the narrower ends of the two dovetails joinedtogether, as shown in FIGS. 3 and 5.

Each groove 14 is defined by a pre-formed component 17, provided alongthe respective longitudinal edge 13 of each segment 11, 12, during themanufacture of that segment. The component 17 may, for example, be madefrom a glass fibre reinforced plastics material. Then, the major part ofeach segment may be moulded to two components 17, that major part beingmade up from inner and outer glass fibre reinforced plastics skins 18,19, with a core 20 of a resin/aggregate mix. The two skins may useunidirectional E-glass fibre stitch-bonded to chopped strand matembedded in a polyester resin and arranged so as to give the maximumhoop-strength to the finished segment.

As shown in FIG. 1, one end of each segment 11, 12 is profiled toprovide a part of a socket 22 so that when the two segments areassembled, a complete socket is formed around one end of the section.The internal diameter of that socket should be slightly greater than theouter diameter of the section, ignoring the region of increasedthickness along the long edges 13. At the other end of the segment, theregion of increased thickness is cut away, so that the outer surface ofthe completed section is circular, as indicated at 23, to form a spigotwhich may be received in a socket of the next adjacent pipe section,during assembly.

Within the spigot region of each segment, and opening into both longedges of the segment are two pockets 25. As shown in FIG. 1, thosepockets extend from the radial end face 26 at the spigot along thelength of the segment and slightly overlap the region of increasedthickness. Thus, when the two segments are connected together as shownin FIG. 1, the respective pairs of pockets 25 mate to provide a singlepocket within the thickness of the adjoining segments. This singlepocket is, during assembly, filled with a mastic sealant, in order toimpart water-tightness to this region of the assembled pipe section.

The pipe is assembled in a sewer to form an internal lining by carryingthe segments along a sewer from an access point and then maneuveringinto position the segments, two at a time to form complete liningsections. Each section is completed by injecting a setting or curingsealant compound into the aligned grooves 14 of adjacent edges 13 tocast in-situ the interlock member 15 to complete a joint between thoseedges. Conveniently, the injection is achieved by vacuum drawing thecompound along the length of the aligned grooves, for example byconnecting a vacuum pump at one end of those grooves and injecting thecompound from the other end. During this process, the compound alsotends to flow between the adjoining edges 27 (FIG. 3) thereby to give avery strong and water-tight joint.

Mastic is injected into the mating pockets 25 from the radial end face26, to complete the seal between the segments, in this region. Oncecompleted, the assembled section is pushed axially fully to engage thespigot portion 23 with the socket 22 of a previously assembled section.A sealant, sealing member or a gasket may be provided within the socket22 following the completion of a section, so that on pressing thereduced diameter portion of the next section into the socket, awater-tight seal between the two pipe sections is formed.

Finally, a grouting material such as a cement-based grout is injectedinto the space between the internal wall of the existing sewer and theexternal surface of the assembled section, so integrating the sectionwith the existing sewer. Preferably, the section is approximatelycentred within the sewer. This may be achieved by wedging the section asappropriate during assembly.

An alternative assembly technique may be appropriate for theconstruction of a sewer lining from pipe sections each having only twosegments, as shown in the drawings. Following the completion of one pipesection, with the socket end exposed for the connection thereto of thenext section, a suitable mastic or gasket is applied around the internalsurface of that socket. Then, a pipe segment is fitted into that socket,whereafter the second pipe segment (which completes the next pipesection) is also fitted into that socket with its edges in alignmentwith the already positioned segment. To permit the setting or curingsealant compound to be injected into the grooves, holes may be drilledinto the grooves from the end of the pipe section adjacent the socket ofthe previously assembled section, the compound then being injected intothose holes whilst a vacuum is drawn from the exposed other ends of thegrooves. Mastic may be injected into the mating pockets at the spigotend, which pockets lie mostly within the confines of the socket of thepreviously assembled pipe section, by drilling holes into the pocketsfrom within the pipe section and injecting the mastic through thoseholes.

FIG. 5 is a cross-section through the enlarged thickness longitudinaljoint, including the cast in-situ interlocking member 15. Also shown inthis figure is an optional reinforcing strip 30 which overlaps thelongitudinal joint, externally of the two segments. This strip is madeof a fibre-reinforced plastics sheet material and is bonded initially toone segment by a suitable adhesive so as to project from thelongitudinal edge thereof. Then, during assembly, the strip 30 is bondedto the other segment, before the in-situ casting of the interlockingmember 15.

In addition to reinforcing the strength and integrity of the pipesection, the strip has the additional function of assisting containingthe compound in the grooves 14 during the injection thereof. Thisfunction may be enhanced if a corresponding strip is fitted to theinternal surfaces of the segments, as well (not shown).

1. A pipe construction system comprising: a plurality of pipe sections,wherein each said pipe section is assembled from a plurality of pipesegments and has a socket formed at one end of the pipe section and aspigot formed at another end of the pipe section, such that the socketof one pipe section receives the spigot of another pipe section toprovide a length of pipe; wherein each said pipe segment has asocket-forming end, a spigot-forming end, and two edges parallel to thelength of the pipe section; wherein each edge includes a region ofincreased radial thickness radially extending beyond the radialthickness of a major part of the pipe segment and wherein each edge hasa groove opened only at said edge and disposed within the radialthickness of the entire pipe segment at said region of increased radialthickness, said region of increased radial thickness extending throughthe socket-forming end and up to the spigot-forming end of the pipesegment, and wherein the spigot-forming end of the pipe segment has aradial thickness equated with said radial thickness of said major partof the pipe segment and has a pocket formed therein within the radialthickness of the major part of the pipe segment, such that each pocketmates with a corresponding pocket of an adjacent pipe segment, wherein asealant is disposed in the mated pockets.
 2. A pipe construction systemas claimed in claim 1, wherein each said groove is of re-entrant form,whereby an interlocking member is cast in-situ in the aligned grooves ofadjacent pipe segments, mechanically to hold those edges together. 3.The pipe construction system as claimed in claim 2, wherein each grooveis of dovetail form, in cross-section.
 4. The pipe construction systemas claimed in claim 1, wherein the region of increased radial thicknessand defining said groove comprises a pre-formed component bonded to thematerial of the major part of the segment during the manufacturethereof.
 5. The pipe construction system as claimed in claim 4, whereinthe major part of each segment comprises a fibre-reinforced plasticsmaterial moulding.
 6. The pipe construction system as claimed in claim4, wherein the major part of each segment comprises inner and outerskins of a fibre-reinforced plastics material between which is disposeda resin-impregnated filler.
 7. The pipe construction system as claimedin claim 1, wherein a reinforcing strip extends along and projects fromthe longitudinal edge region of one pipe segment, for bonding to thecorresponding edge region of an adjacent pipe segment.
 8. A method ofconstructing a pipe comprising: assembling a pipe section from aplurality of pipe segments, the pipe section having a socket formed atone end of the pipe section and a spigot formed at another end of thepipe section, and each pipe segment having a socket-forming end, aspigot-forming end, and two edges parallel to the length of the pipesection; wherein each edge includes a region of increased radialthickness radially extending beyond the radial thickness of a major partof the pipe segment and wherein each edge has a groove opened only atsaid edge and disposed within the radial thickness of the entire pipesegment at said region of increased radial thickness, the region ofincreased radial thickness extending through the socket-forming end andup to the spigot-forming end of the pipe segment, and wherein thespigot-forming end of the pipe segment has a radial thickness equatedwith the radial thickness of the major part of the pipe segment and hasa pocket formed therein within the radial thickness of the major part ofthe pipe segment; wherein the step of assembling a pipe section includesthe steps of mating the pockets of adjacent pipe segments; injecting asealant into the pockets at the spigot end of the pipe section; aligningthe grooves along the edges of adjacent pipe segments; and injecting asealant into each pair of aligned grooves and allowing the sealant tocure, thereby providing a bonding interlocking member; assemblingadditional pipe sections in a like manner; and continuouslyinterengaging the spigot end of a pipe section into the socket end ofanother pipe section to provide a desired length of pipe; wherein thestep of continuously interengaging includes at least one of the steps ofdisposing a sealant internally around the socket of a pipe section toreceive the spigot of an another pipe section; and disposing a sealantexternally around the spigot of a pipe section to be received by thesocket of another pipe section.
 9. The method as claimed in claim 8,wherein the step of injecting a sealant into the aligned groovesincludes the step of drawing a vacuum through the grooves from one endof the pipe section while injecting the sealant into the grooves fromthe other end of the section.
 10. The method as claimed in claim 9,wherein the step of assembling further includes permitting the sealantto flow between the interfacing edges of the respective pipe segments.11. The method as claimed in claim 8, wherein the pockets open into theradial end face of the pipe section, and wherein the step of injectingthe sealant into the pockets including injecting a sealing agent intothose pockets from said end face.
 12. The method as claimed in claim 8,wherein said sealant comprises a non-setting mastic.
 13. The method asclaimed in claim 8, wherein said sealant comprises a sealing gasketfitted either around the spigot or internally within the socket.
 14. Themethod as claimed in claim 8, further comprising the step of securing areinforcing strip to at least one of the internal and external adjacentedge regions of two segments to bridge the longitudinal joint.
 15. Themethod of constructing a pipe as claimed in claim 8, further comprising:lining an existing closed duct by effecting within the existing duct themethod of constructing a pipe as claimed in claim 8 so as to build-upthe pipe in situ in the duct but with a clearance between an outer wallof the pipe and an inner wall of the duct, and then filling saidclearance with a grouting material.
 16. A method of constructing a pipecomprising: assembling a pipe section from a plurality of pipe segments,the pipe section having a socket formed at one end of the pipe sectionand a spigot formed at another end of the pipe section, and each pipesegment having a socket-forming end, a spigot-forming end, and two edgesparallel to the length of the pipe section; wherein each edge includes aregion of increased radial thickness radially extending beyond theradial thickness of a major part of the pipe segment and wherein eachedge has a groove opened only at said edge and disposed within theradial thickness of the entire pipe segment at said region of increasedradial thickness, the region of increased radial thickness extendingthrough the socket-forming end and up to the spigot-forming end of thepipe segment, and wherein the spigot-forming end of the pipe segment hasa radial thickness equated with the radial thickness of the major partof the pipe segment and has a pocket formed therein within the radialthickness of the major part of the pipe segment; wherein the step ofassembling a pipe section includes the steps of mating the pockets ofadjacent pipe segments; injecting a sealant into the pockets at thespigot end of the pipe section; aligning the grooves along the edges ofadjacent pipe segments; and injecting a sealant into each pair ofaligned grooves and allowing the sealant to cure, thereby providing abonding interlocking member; selectively disposing a sealant eitherinternally around the socket of the pipe section or externally aroundthe spigot of the pipe section; and selectively fitting either thespigot-forming ends of a plurality of other pipe segments into thesocket of the assembled pipe section or the socket-forming ends of aplurality of other pipe segments around the spigot end of a pipesection, while mating the pockets of adjacent pipe segments and aligningthe grooves along the edges of adjacent pipe segments, to form a furtherpipe section coupled to the assembled pipe section; injecting a sealantinto the pockets at the spigot end of the further pipe section; andinjecting a sealant into each pair of aligned grooves of the furtherpipe section and allowing the sealant to cure.
 17. The method as claimedin claim 16, wherein the step of injecting the sealant into the groovesof each further pipe section includes forming an opening into thegrooves from internally within the further pipe section adjacent thepreviously-assembled pipe section, and then drawing a vacuum from thegrooves through said opening while injecting the sealant into thegrooves from the other end of the pipe section.
 18. The method asclaimed in claim 17, wherein said sealant is permitted to flow betweenthe interfacing edges of the respective segments.
 19. The method asclaimed in 16, wherein the step of injecting the sealant into thegrooves of each further pipe section includes forming an opening intothe grooves from internally within the further pipe section adjacent thepreviously-assembled pipe section, and then drawing a vacuum from thegrooves from the other end of the pipe section while injecting thesealant into the grooves through said opening.
 20. The method as claimedin claim 16, wherein a further opening is formed from internally withinthe further pipe section into the pockets and a sealing agent isinjected into those pockets through said further opening.
 21. The methodas claimed in claim 20, wherein said sealing agent comprises anon-setting mastic.
 22. The method as claimed in claim 16, wherein areinforcing strip is secured to at least one of the internal andexternal adjacent edge regions of two segments to bridge thelongitudinal joint.
 23. The method of constructing a pipe as claimed inclaim 16, further comprising lining an existing closed duct comprisingby effecting within the existing duct the method of constructing a pipeas claimed in claim 16 so as to build-up the pipe in situ in the ductbut with a clearance between an outer wall of the pipe and an inner wallof the duct, and then filling said clearance with a grouting material.